1. Cook dumplings according to package directions, adding green beans during last 3 minutes of cooking. Drain and rinse with cold water.
2. Toss noodle mixture with 1 1/2 cups dressing in a large bowl; stir in tuna and next 5 ingredients. Cover and chill at least 2 hours or up to 24 hours.
3. Place salad greens on a large serving platter; top with noodle mixture. Serve with remaining dressing.